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Heart scan surprises: CT reveals many non-heart problems, too

17.05.2005

Trained eyes needed to spot small cancers, blood clots and aneurysms early

Nearly half of all patients who get their hearts scanned with a high-speed CT scanner may get a shocking surprise: a diagnosis of a serious problem that has nothing to do with their heart. New research from the University of Michigan shows that 43 of 98 patients who had a CT heart scan to look for clogged arteries were also found to have significant or potentially significant signs of problems with their lungs, blood vessels or organs. These discoveries ranged from possible lung cancer in 16 patients to potentially dangerous blood clots and aneurysms in 10 patients. The results are being presented here today at the American Roentgen Ray Societys annual meeting by cardiac imaging specialists from the U-M Cardiovascular Center.

The researchers say their data show just how important it is for trained radiologists to view heart CT scans, as is done at the U-M Health System, rather than having the scans read by heart specialists alone. They note that there has been explosive growth in the number of patients having CT scans to diagnose or monitor heart disease in recent years. "Many of these patients are having their scans at cardiology centers that may or may not employ a physician who specializes in radiology and has been trained to spot problems of any kind on medical images," says lead author Smita Patel, M.B.B.S., an assistant professor of radiology at the U-M Medical School and member of the U-M thoracic (chest) radiology team. "Our research suggests that may leave potentially serious problems undiagnosed. The trained eyes of radiologists are needed."

The rapid rise in CT heart scans, known as CT coronary angiography or CTCA, has given more patients and their doctors a detailed view of the coronary arteries that feed the heart muscle -- without an invasive procedure. "The new cardiac CT that we can perform today can assess the arteries supplying the heart for blockages without requiring the patient to undergo catheterization, which involves a tube inserted through the groin into the heart to assess these arteries," says Patel. "When the arteries are normal, the patient often does not need to undergo further cardiac testing."

But the scans also reveal the finest details of structures near the heart -- including the lungs, aorta, liver, pancreas and the structures and spaces that surround them. And that level of detail is only increasing as CT scanners become more powerful. Patel and her colleagues looked at images taken with U-Ms 16-slice multidetector CT scanners. But in the last year, U-M and other major centers have acquired even more powerful 64-slice CT scanners that can image the entire chest in just a few seconds, allowing even the fast-moving heart muscle and arteries to be seen clearly.

The simultaneous rapid increases in the precision and utilization of CTCA, says Patels co-author Ella Kazerooni, M.D., makes it important to study the rate at which non-heart problems are found. Kazerooni, a professor of radiology and chief of thoracic radiology at U-M, notes that a smaller study by Johns Hopkins researchers showed that 16 percent of 75 chest pain and heart disease patients had major non-cardiac findings on their CTCA scans. The new U-M results are from a larger group of patients imaged for any reason.

Radiologists have long known that medical images taken for one reason may reveal entirely unrelated problems or suspicious areas. These "incidentalomas," as theyre known, can pose serious questions of whether or not to perform a biopsy or other tests. But the rise in CTCA use by non-radiologists has raised concern that untrained eyes may miss problems outside the heart. Patel and U-M radiologist Naama Bogot, M.D., who read all the scans, found some sort of non-heart abnormality in 61 percent of the patients. Many of these were judged insignificant. But in the 43 patients who had significant or potentially significant findings, the range of severity was wide.

In 16 patients, lung nodules larger than 4 millimeters in diameter showed up -- two of which were later found to be stage 1 lung cancer. Eleven patients were shown to have a potentially serious lung disease, either emphysema or another condition. Four had fluid buildup in the lungs. Twelve patients had enlarged lymph nodes in the chest and three had masses in the upper anterior chest. Twenty patients had fluid in the sac that surrounds the heart; most of them were minor but one was major. Eight patients had an aneurysm or dissection in the upper part of their aorta, and one patient had blood clots threatening to block arteries in his lungs.

Since the upper part of the abdomen is visible when imaging the lower part of the heart during CT scanning, the researchers were also able to see potential problems there. Seven patients had lesions on their livers, one had a mass in his or her pancreas, and other patients had other findings. In all, Patel says, the high rate of non-heart findings drives home the importance of having a team-based approach to reading CTCA scans. At U-M, cardiologists and thoracic radiologists routinely take this cooperative approach.

The American College of Radiology has just issued a Clinical Statement on Noninvasive Cardiac Imaging online that will be published in the June issue of the journal Radiology. It calls for specialized training, education and levels of experience for both radiologists who read CTCA images and the technologists who conduct the scans. Performing diagnostic-quality scans requires fine-tuning of the scanning parameters that relies on the combined expertise of the radiologist and technologist.

Meanwhile, Patel and her U-M colleagues are currently performing research that directly compares CTCA and coronary angiograms performed in the traditional way, using a catheter that is threaded into the coronary arteries to inject dye that can be seen on X-ray images. This kind of research, supported in part by an RSNA Research Scholar Award won by Patel, is needed to help settle the debate over the relative merits of both imaging techniques.

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